Acetylcholine analogs will be synthesized and will be tested for activity at cholinergic receptor sites in Schistosoma mansoni. The testing will include physiological measurements of motor activity, biochemical measurements of acetylcholinesterase, and histochemical measurements of the binding of fluorescent acetylcholine analogs to the nervous system of schistosomes. The compounds will also be tested in standard mammalian systems. Structure-activity relationships will be determined, suggesting what molecular variations may lead to selective high affinity for the receptors in schistosomes. This information will be used to guide the synthesis of further compounds. It is hoped that this process can ultimately lead to a method for the rational development of drugs for the treatment of schistsomiasis.